The present disclosure relates to annealing systems and methods for processing microelectronic workpieces, and in particular, systems and methods for annealing one or more layers containing magnetic material on microelectronic workpieces.
Semiconductor device formation involves a series of manufacturing techniques related to the formation, patterning and removal of a number of layers of material on a substrate. Magnetic annealing is one of three processes required to manufacture magnetoresistive random access memory (MRAM) devices compatible with conventional complementary metal oxide semiconductor (CMOS) logic based microelectronic workpieces. To successfully anneal a workpiece, the ferromagnetic layer must be held at a predetermined temperature in a magnetic field for a period of time long enough for the crystals to orient themselves in a common direction upon cooling. This process, which is also referred to as “soak” is carried out in an inert, reducing, or vacuum environment to prevent oxidation of the workpieces, while they are held at the predetermined temperature.
Magnetic annealing equipment generally operates in batch-mode, i.e., plural workpieces are annealed at the same time, and performs a sequence of steps. As an example, these steps include heating, soaking, and cooling the workpieces in the presence of a magnetic field, typically between 0.02 and 7.0 T (Tesla). The cost of MRAM device manufacturing is linked to the magnetic annealing tools, where the productivity (acceptable devices produced per hour) is the product of density (number of devices per workpiece), throughput (workpieces per hour), and yield (ratio of acceptable devices to total number of devices processed), as dictated by the overall thermal/anneal cycle.
Conventionally, magnetic annealing systems for in-plane and out-of-plane magnet orientation are of either a horizontal or vertical orientation. And, with manufacturing facility floor-space being a premium, tool footprint and workpiece throughput, as mentioned above, are critical for successful implementation.